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Keywords:

  • polyclonal persistent B lymphocytosis (PPBL);
  • marginal zone;
  • phenotypic study;
  • IgVH gene somatic mutations

Summary.  Persistent polyclonal B-cell lymphocytosis (PPBL) is an unusual and benign lymphoproliferation characterized by a polyclonal expansion of B lymphocytes, whose nature remains undetermined. The phenotypic analysis of three cases revealed that these cells were CD27+ IgMhigh CD21high CD5low and CD23low, a phenotype associated with the normal marginal zone (MZ) B-cell compartment. As MZ B cells have initiated immunoglobulin (Ig)V gene somatic mutations, PPBL IgVH genes were sequenced. An average of 73% of these sequences were mutated. The mean number of mutation per sequence was 6·9, a number similar to those observed in the MZ B-cell compartment.